You can minimize the effects of automated spam by employing the use of
a CAPTCHA. While Nitrogen's postback mechanism itself helps to minimize
automated POST-based spam, more aggressive Javascript enabled bots or
bots written targetting Nitrogen-based sites.

For this, you can integrate a Recaptcha element into your application's
postbacks. You just need to add a #recaptcha{} element and a
recaptcha_event/2 function to your page, and you're ready to go.